MagicDisc does mount ISOs. I use it all the time. Sometimes when you already have an image mounted you need to unmount all images then mount the ISO. Also MagicDisc installs a unsigned driver that may have been blocked by either windows or your anti-virus.

I would fist disable your AV then try to mount an ISO, if that doesn't work, uninstall the program and re-install. Accept any prompts that alerts you to install unsigned drivers being installed.

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